The present invention relates to an automotive vehicle, especially an industrial vehicle. More specifically, the invention concerns a rear aerodynamic device for a vehicle and a vehicle equipped with such a device.
For many years, attempts have been made to improve vehicle efficiency. One factor in an efficient design is the aerodynamic characteristics of a vehicle. The air drag of a vehicle and especially of an industrial vehicle such as a truck is one of the factors that has a direct impact on fuel consumption. Therefore, in a general trend towards rare and expensive energy—whether fossil or not—, aerodynamics is one of the key issue in an efficient vehicle.
One problem with the current industrial vehicles is that air passing longitudinally rearward along the side walls of the vehicle tends to deviate outward behind the vehicle rear wall. Such an air path is riot favourable because it causes turbulence and, moreover, contributes to the creation of a low pressure area behind the vehicle. This makes the drag coefficient of the vehicle high, which, consequently, generates a high fuel consumption.
Several devices have been added to vehicles in order to reduce turbulence, to prevent air from deviating away from the vehicle walls and/or to bring air into the rear low pressure area. However, these devices don't make it possible to efficiently canalize air, and they may create turbulence in other locations. Moreover, many of these known devices cannot be properly integrated into the general structure of the vehicle.
It therefore appears that, from several standpoints, there is room for improvement in industrial vehicles aerodynamics.
It is desirable to provide an improved vehicle, which can overcome the drawbacks encountered in conventional vehicle.
It is also desirable to provide a vehicle with a lower aerodynamic drag.
According to an aspect of the invention an aerodynamic device is provided that is suitable to be located under a rear end of a cargo body of an industrial vehicle, said device comprising a nozzle having an inlet positioned on a lateral external face of the device and capable of canalising air flowing along the vehicle and an outlet positioned at the rear part of the device and capable of ejecting the air flow underneath a vehicle rear face.
Consequently, when the device is fastened under a vehicle and when this vehicle is in motion, the air flowing in parallel with the vehicle side wall, along the wheels, is canalized through the nozzle and discharged behind the vehicle rear wall. This has two main advantages. First of all, turbulence is considerably lessened, because the nozzle ensures that the air flow has a steady direction. Moreover, due to the air discharged behind the vehicle rear wall, the pressure in the area located just behind the vehicle is increased. These two technical effects resulting from the nozzle contribute to efficiently decrease the aerodynamic drag of the vehicle and, as a consequence, to decrease the fuel consumption. One of the specific problems of industrial vehicles is their substantially parallelepiped shape. To maximise the vehicle cargo it is not possible to depart from an angular shape which is however not desirable in terms of aerodynamics. The invention has a positive impact on the aerodynamic drag insofar as the invention makes it possible to channel a flow of air towards the vehicle rear wall which is inherently a source of turbulence. The air flow that is ejected under the vehicle rear wall helps decreasing the aerodynamic drag.
The device according to an aspect of the invention ensures that the air flow is properly canalized from the vehicle side towards the vehicle back, i.e. from the nozzle inlet towards the nozzle outlet and, moreover, that this air flow does not undergo multiple and/or sudden direction changes. Therefore, said device proves to be very effective and to considerably improves the vehicle aerodynamics.
It has to be noted that the device is described in its position when fastened under a vehicle frame, the terms “side”, “front”, “rear”, “upper”, “lower”, “inner”, “outer”, etc. being used to designate parts of the device in said position.
Preferably, the nozzle inlet is located in the vicinity of the nozzle outlet, so that said device can be secured onto the vehicle frame rearward from an axle of said vehicle.
This makes it possible to fit the aerodynamic device according to the invention on existing vehicles.
According to a preferred implementation of the invention, the nozzle cross section increases from the inlet towards the outlet, which contributes to increase the pressure behind the vehicle.
At least one among an inner wall and an outer wall of the nozzle may be convergent inwardly rearward. This shape generates an air flow which reduces the device and the vehicle wake, i.e. which reduces the zone of turbulence. Preferably both inner wall and outer wall are convergent, with the outer wall being less convergent, so that the nozzle cross section increases from the inlet towards the outlet. Preferably as well, the inner wall and/or the outer wall of the nozzle can be curved, in order to enhance the air guiding
Besides, for the same reason, at least one among a lower wall and an upper wall of the nozzle may be convergent upwardly rearward. For example, the nozzle upper wall can be substantially horizontal, so that the device can be more easily fastened under the vehicle frame, and the nozzle lower wall can be convergent. Preferably, at least the lower wall is properly curved to enhance the air guiding.
Therefore, in an advantageous way, the nozzle and the device can be streamlined as a boat tail, which considerably improves the aerodynamics.
According to an embodiment of the invention, the device further comprises a ridge extending under the nozzle at the lower part of the device, said ridge extending roughly longitudinally and its external side wall converging inwardly rearward, whereby said ridge can canalize the residual air that did not enter the nozzle, and direct it rearward and inwardly. This important arrangement ensures that, when the device is fastened under the vehicle, the residual air flow is directed towards the vertical longitudinal plane of symmetry of the vehicle. Said ridge performs the functions of collecting the air not moving inside the nozzle, and to guide it in an appropriate direction in order to minimize turbulence.
Said ridge may have an internal side wall diverging outwardly rearward.
In an advantageous way, the device has a lower surface which is convergent upwardly rearward, this shape being favourable for the air flow since it reduces the wake.
It can be envisaged that the device form a substantially parallelepiped block having a vertical longitudinal plane of symmetry, said device comprising only two nozzles each located near a side of the block. Said device can thus extend over the entire width of the vehicle frame, so as to canalize air flowing along both sides of the vehicle.
There may be provided on the device two ridges defining a central diverging passageway below the device, when each ridge has an internal side wall diverging outwardly rearward. This contributes to increase the pressure behind the vehicle, because the air speed decreases in the diverging passageway.
The central passageway may further comprise substantially longitudinally extending fins projecting downwards, thereby helping the air flow guiding.
The invention also concerns a vehicle such as a trailer, a semi-trailer or a straight truck comprising a frame supported by wheels and a cargo body, which further comprises an aerodynamic device as previously described, said device being located under a rear end of the cargo body, rearward from the wheels. With this arrangement, the invention makes it possible to improve the vehicle aerodynamics without requiring a device which takes up a large area and/or volume under the vehicle.
Preferably, the vehicle comprises a side panel fastened to the frame, along and outside the wheels, said panel being arranged to form a substantially continuous and smooth surface with the nozzle inner wall. This fairing contributes to efficiently guide air in order to further decrease turbulence and improve aerodynamics.
According to an embodiment of the invention, the vehicle can further comprise an underride guard extending in the transverse direction; the said underride guard (30) is integrated in said aerodynamic device (10), under the nozzles (15).
It therefore appears that the device of the invention can improve the vehicle aerodynamics without hampering the implementation of other conventional elements of the vehicle, such as security organs. Furthermore, such organs can fit corresponding arrangements of the aerodynamic device according to the invention, which is very convenient and makes the assembly of the vehicle easier and faster.
According to an embodiment of the invention, the vehicle can also comprise at least one wing extending from a rear edge of the cargo body and substantially located in a plane converging towards the median longitudinal axis of the vehicle. Preferably, the vehicle is provided with four wings extending each from a rear edge of the cargo body. This or these wings form behind the vehicle a shape that reduces the wake.
It can be envisaged that the vehicle comprise at least one side wing extending from a vertical rear edge of the cargo body, said wing extending downwards substantially as far as the nozzle lower wall, in the prolongation of the nozzle outer wall. This improves the air guiding by preventing the air flow to deviate outwardly downstream the nozzle outlet.
These and other advantages will become apparent upon reading the following description in view of the drawing attached hereto representing, as non-limiting examples, embodiments of a vehicle according to the invention.